Integrated structures containing vertically-stacked memory cells

ABSTRACT

Some embodiments include an integrated structure having a stack of alternating dielectric levels and conductive levels, and having vertically-stacked memory cells within the conductive levels. An opening extends through the stack. Channel material is within the opening and along the memory cells. At least some of the channel material contains germanium.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 15/677,914 which was filed Aug. 15, 2017, which is a continuation ofU.S. patent application Ser. No. 14/827,695 which was filed Aug. 17,2015, now U.S. Pat. No. 9,761,599, each of which is hereby incorporatedby reference.

TECHNICAL FIELD

Integrated structures containing vertically-stacked memory cells.

BACKGROUND

Memory provides data storage for electronic systems. Flash memory is onetype of memory, and has numerous uses in modern computers and devices.For instance, modern personal computers may have BIOS stored on a flashmemory chip. As another example, it is becoming increasingly common forcomputers and other devices to utilize flash memory in solid statedrives to replace conventional hard drives. As yet another example,flash memory is popular in wireless electronic devices because itenables manufacturers to support new communication protocols as theybecome standardized, and to provide the ability to remotely upgrade thedevices for enhanced features.

NAND may be a basic architecture of integrated flash memory, and may beconfigured to comprise vertically-stacked memory cells. It is desired todevelop improved NAND architecture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view of an example embodimentintegrated structure.

FIG. 2 is a diagrammatic top-down view of the example embodimentintegrated structure of FIG. 1, and is a view along the line 2-2 of FIG.1.

FIGS. 3-10 are diagrammatic cross-sectional views of example embodimentintegrated structures.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some embodiments include utilization of germanium or silicon/germaniumwithin the channel material of vertical NAND configurations. Germaniumhas better mobility than the silicon conventionally utilized for thechannel material, which may improve current conduction along a NANDstring. Example embodiments are described with reference to FIGS. 1-10.

Referring to FIG. 1, a semiconductor construction (i.e., integratedstructure) 10 is shown to comprise a stack 15 of alternating first andsecond levels 18 and 20. The levels 18 may be dielectric, and the levels20 may be conductive. The conductive levels 20 may comprise, forexample, one or more of various metals (for example, tungsten, titanium,etc.), metal-containing compositions (for example, metal nitride, metalcarbide, metal silicide, etc.), and conductively-doped semiconductormaterials (for example, conductively-doped silicon, conductively-dopedgermanium, etc.). For instance, the conductive levels 20 may comprisen-type doped polycrystalline silicon (i.e., n-type doped polysilicon).The dielectric levels 18 may comprise any suitable composition orcombination of compositions; and may, for example, comprise silicondioxide.

The levels 18 and 20 may be of any suitable thicknesses; and may, forexample, have thicknesses within a range of from about 5 nm to about 300nm. In some applications, the levels 18 may be thinner than the levels20. For instance, levels 18 may be about 20 nm thick and levels 20 maybe about 30 nm thick.

Charge-storage material 24 is adjacent the conductive levels 20, and isspaced from the conductive material of levels 20 by charge-blockingmaterial 22.

The charge-storage material 24 may comprise any suitable composition orcombination of compositions; and in some embodiments may comprisefloating gate material (for instance, doped or undoped silicon) orcharge-trapping material (for instance, silicon nitride, metal dots,etc.).

The charge-blocking material 22 may comprise any suitable composition orcombination of compositions; and in some embodiments may comprise one ormore of silicon dioxide, hafnium oxide, zirconium oxide, siliconnitride, etc.

Gate dielectric 26 is adjacent charge-storage material 24. The gatedielectric may comprise any suitable composition or combination ofcompositions; and in some embodiments may comprise, for example, silicondioxide.

An opening 27 extends through the stack 15, and in the shown embodimentsuch opening is entirely filled with channel material 28. The channelmaterial comprises germanium. For instance, the channel material maycomprise Si_((1-x))Ge_(x); where x is a number greater than zero, andless than or equal to 1. In some embodiments, the channel material maycomprise, consist essentially of, or consist of, silicon and germanium.The germanium may be present to, for example, a concentration within arange of from about 5 atomic percent to about 80 atomic percent. Asanother example, the germanium may be present to a concentration withina range of from about 10 atomic percent to about 30 atomic percent.

In some embodiments, the channel material may comprise one or moredopants. In such embodiments, the dopants may be p-type, n-type and/ori-type.

The various materials 22, 24 and 26, together with regions of conductivelevels 20 and channel material 28, form a first series ofvertically-stacked memory cells 30 a and 30 b, and a second series ofvertically-stacked memory cells 31 a and 31 b. The vertically-stackedmemory cells 30 a and 30 b may be considered to form a first NANDstring, and the vertically-stacked memory cells 31 a and 31 b may beconsidered to form a second NAND string. The memory cells may beconsidered to be within the conductive levels 20 (i.e., elevationallycoextensive with the conductive levels) in the illustrated embodiment.

The number of memory cells in each vertical string is determined by thenumber of conductive levels 20. The stack may comprise any suitablenumber of conductive levels. In some embodiments, the stack 15 maycomprise 8 conductive levels, 16 conductive levels, 32 conductivelevels, 64 conductive levels, 1024 conductive levels, etc.

The cross-section section of FIG. 1 shows opening 27 having two opposingsidewalls 23 and 25. However, the opening may have a closed shape whenviewed from above so that such sidewalls actually merge into a singlecontinuous sidewall. For instance, the opening may have a circularshape, elliptical shape, polygonal shape, rectangular shape, etc. whenviewed from above. FIG. 2 shows an example embodiment of an opening 27having a closed shape when viewed from above. In the embodiment of FIG.2, the sidewalls 23 and 25 are part of a single continuous sidewallextending around the closed shape of opening 27.

The channel material 28 of FIG. 1 is shown comprising a homogeneouscomposition throughout. In other embodiments, the channel material maycomprise a gradient of germanium concentration and/or a gradient ofdopant concentration. For instance, FIGS. 3 and 4 show constructions 10a and 10 b, respectively, comprising horizontally-extending gradients ofgermanium concentration.

Referring to FIG. 3, the channel material has exterior surfaces 33 and35 along the sidewalls 23 and 25, respectively, of the opening 27. Thechannel material also comprises an interior region 36 between theexterior surfaces, with the interior region being horizontally offsetfrom the exterior surfaces. In the shown embodiment, the germaniumconcentration [Ge] increases along directions from the interior regionto the exterior surfaces as indicated by arrows 36 and 38.Alternatively, the embodiment of FIG. 3 may be considered to illustratedecreasing germanium concentration along directions from the exteriorsurfaces 33 and 35 toward the interior region 36.

The germanium concentration gradient may increase from any suitablefirst concentration to any suitable second concentration. For instance,in some embodiments the first concentration may be about 0 atomicpercent germanium and the second concentration may be about 100 atomicpercent germanium. As another example, the first concentration may beabout 0 atomic percent germanium and the second concentration may beabout 85 atomic percent germanium. As another example, the firstconcentration may be about 5 atomic percent germanium and the secondconcentration may be about 85 atomic percent germanium. As anotherexample, the first concentration may be about zero atomic percentgermanium and the second concentration may be about 30 atomic percentgermanium. As another example, the first concentration may be about 10atomic percent germanium and the second concentration may be about 30atomic percent germanium.

FIG. 4 shows an embodiment similar to that of FIG. 3, but in which thegermanium concentration [Ge] increases along directions from theexterior surfaces 33 and 35 toward the interior region 36 of the channelmaterial 28, as indicated by arrows 40 and 42. The germaniumconcentration gradient may increase from any suitable firstconcentration to any suitable second concentration. For instance, insome embodiments the first concentration may be about 0 atomic percentgermanium and the second concentration may be about 100 atomic percentgermanium. As another example, the first concentration may be about 0atomic percent germanium and the second concentration may be about 85atomic percent germanium. As another example, the first concentrationmay be about 5 atomic percent germanium and the second concentration maybe about 85 atomic percent germanium. As another example, the firstconcentration may be about zero atomic percent germanium and the secondconcentration may be about 30 atomic percent germanium. As anotherexample, the first concentration may be about 10 atomic percentgermanium and the second concentration may be about 30 atomic percentgermanium.

The embodiments of FIGS. 3 and 4 may advantageously enable channelmaterial properties to be tailored for specific applications in order tohave desired electrical, physical and/or chemical properties along thememory cells 30 a, 30 b, 31 a and 31 b. For instance, it may be desiredto have an appropriate balance between germanium concentration andsilicon concentration within the channel material along the memory cellsin order to achieve desired electrical mobility and semiconductorproperties.

Although the embodiments of FIGS. 3 and 4 specifically illustratehorizontal gradients of germanium concentration, in other embodimentsthere may also be horizontal gradients of dopant concentration (forinstance, horizontal gradients of p-type dopant, n-type dopant and/ori-type dopant). The dopant gradients may extend along the samedirections as the germanium gradients, or may be oppositely orientedrelative to the germanium gradients.

The embodiments of FIGS. 1-4 show germanium-containing material 28entirely filling opening 27. In other embodiments, liners may beprovided along sidewalls of the opening prior to filling the openingwith channel material 28. For instance, FIG. 5 shows a construction 10 chaving liners 44 and 46 along the sidewalls of opening 28. Although twoliners are illustrated in the cross-section section of FIG. 5, it is tobe understood that the opening may have a closed shape (as describedwith reference to FIG. 2), and accordingly the illustrated liners may bepart of a single liner which extends entirely around the closed shape ofthe opening.

The liners 44 and 46 comprise liner material 45. Such liner material maybe a non-germanium-containing material. In some embodiments, the linermaterial may be non-germanium-containing semiconductor material (and inparticular embodiments may be a wide band-gap containing semiconductormaterial). For example, the liner material may comprise silicon (whichmay be monocrystalline, polycrystalline, amorphous, etc.), III/Vsemiconductor material, II/VI semiconductor material, etc. For instance,the liners may comprise silicon carbide, gallium arsenide, zinc oxide,indium oxide, tin oxide, etc. The liners may be doped in someembodiments, and in other embodiments may be undoped.

In the embodiment of FIG. 5, the material 28 may be considered agermanium-containing material which is spaced from sidewalls 23 and 25of opening 27 by the non-germanium-containing material 45 of liners 44and 46. The germanium-containing material 28 may be homogeneous, or maycomprise horizontally-extending germanium gradients of the typesdescribed above with reference to FIGS. 3 and 4.

The liners 44 and 46 may have any suitable thicknesses, and in someembodiments may have thicknesses within a range of from about onemonolayer to about 60 Å, thicknesses within a range of from about 20 Åto about 50 Å, etc.

The liners may advantageously enable channel material properties to betailored for specific applications. For instance, in some embodimentsthe liners may be kept thin enough so that channel conduction ofvertically-stacked memory cells (e.g., memory cells 30 a, 30 b, 31 a and31 b) extends through the semiconductor material of the liners, and alsothrough a region of the germanium-containing material 28 adjacent theliners (as shown). Accordingly, the compositions of the liners and thegermanium-containing material 28 may be independently adjusted to tailorelectrical, physical and/or chemical properties for specificapplications. In some embodiments, the liners may increase a distancefrom tunnel dielectric 26 of the memory cells (e.g., 30 a, 30 b, 31 aand 31 b) to channel material 28, which may reduce coulombic scattering.

The embodiments of FIGS. 1-5 show a central region of opening 27entirely filled with channel material. In other embodiments, the centralregion of the opening may comprise insulator (which may be, for example,air, silicon dioxide, etc.), as described below with reference to FIGS.6-10.

Referring to FIG. 6, a construction 10 d is shown to comprisegermanium-containing liners 48 and 50 along the sidewalls 23 and 25 ofopening 27, with such liners only partially filling the opening to leavea hollow. The construction further comprises insulator 52 between theliners 48 and 50 and within the hollow. The insulator 52 may include gas(for instance, air). Additionally, or alternatively, the insulator mayinclude semisolid or solid material (for instance, silicon dioxide,silicon nitride, etc.).

The liners 48 and 50 may have any suitable thicknesses T; and in someembodiments may have thicknesses within a range of from about 2nanometers (nm) to about 50 nm.

The germanium-containing material 28 of liners 48 and 50 may compriseany of the compositions described above with reference to thegermanium-containing material 28 of FIG. 1. The germanium-containingmaterial 28 of the liners 48 and 50 may be homogeneous (as shown in FIG.6), or may comprise horizontally-extending gradients of germaniumconcentration. For instance, FIGS. 7-9 show constructions 10 e, 10 f and10 g, respectively, comprising horizontally-extending gradients ofgermanium concentration.

Referring to FIG. 7, the germanium-containing liner 48 has exteriorsurfaces 49 and 51, and similarly the germanium-containing liner 50 hasexterior surfaces 53 and 55; with the surfaces 51 and 55 being adjacentinsulator 52, and the surfaces 49 and 53 being along sidewalls ofopening 27. In the shown embodiment, the germanium concentration [Ge]increases along directions from the insulator to the sidewalls ofopening 27 as indicated by arrows 56 and 58. The germanium concentrationgradient may increase from any suitable first concentration to anysuitable second concentration, and may, for example, comprise any of theconcentration gradients described above with reference to FIGS. 3 and 4.

The liners 48 and 50 may be considered to comprise interior regions 60and 62 respectively (with such interior regions being inward of theexterior surfaces, and thus being horizontally-offset relative to theexterior surfaces), and the embodiment of FIG. 7 may be considered toillustrate decreasing germanium concentration along directions from theexterior surfaces 49 and 53 toward the interior regions 60 and 62.

FIG. 8 shows an embodiment similar to that of FIG. 7, but in which thegermanium concentration [Ge] increases along directions from theexterior surfaces 49 and 53 toward the interior regions 60 and 62 of thegermanium-containing liners, as indicated by arrows 64 and 66. Thegermanium concentration gradient may increase from any suitable firstconcentration to any suitable second concentration, and may, forexample, comprise any of the concentration gradients described abovewith reference to FIGS. 3 and 4.

FIG. 9 shows an embodiment in which the germanium concentration [Ge]within each of the germanium-containing liners increases alongdirections from exterior surfaces toward interior regions as indicatedby arrows 90-93. The germanium-containing liner 48 may be considered tocomprise a first exterior surface 49 along the sidewall of opening 27, asecond exterior surface 51 along the insulator-filled hollow, and aninterior region 60 between the first and second exterior surfaces. Thegermanium concentration within liner 48 may be considered to increasealong a first direction from the first exterior surface 49 to theinterior region 60, as indicated by the arrow 90; and also to increasealong a second direction from the second exterior surface 51 to theinterior region 60 as indicated by the arrow 91. Thegermanium-containing liner 50 may be similarly considered to comprise afirst exterior surface 53, a second exterior surface 55, and an interiorregion 62 between the first and second exterior surfaces. The germaniumconcentration within liner 50 may be considered to increase along afirst direction from the first exterior surface 53 to the interiorregion as indicated by the arrow 93, and to increase along a seconddirection from the second exterior surface 55 to the interior region 62as indicated by the arrow 92.

An advantage of the configuration of FIG. 9 may be that such enablescharge to be carried along quantum wells within liners 48 and 50 duringutilization of NAND strings.

The embodiments of FIGS. 7-9 may advantageously enable channel materialproperties to be tailored for specific applications in order to havedesired electrical, physical and/or chemical properties along the memorycells 30 a, 30 b, 31 a and 31 b. For instance, it may be desired to havean appropriate balance between germanium concentration and siliconconcentration within the channel material along the memory cells inorder to achieve desired electrical mobility and semiconductorproperties.

Although the embodiments of FIGS. 7-9 specifically illustrate horizontalgradients of germanium concentration, in other embodiments there mayalso be horizontal gradients of dopant concentration (for instance,horizontal gradients of p-type dopant, n-type dopant and/or i-typedopant). The dopant gradients may extend along the same directions asthe germanium gradients, or may be oppositely oriented relative to thegermanium gradients.

In some embodiments, the germanium-containing liners of FIGS. 6-9 may beutilized in combination with the non-germanium-containing liners of FIG.5. For instance, FIG. 10 shows a construction 10 h which comprisesnon-germanium-containing liners 44 and 46 utilized together withgermanium-containing liners 48 and 50. The liners 44 and 46 comprise theliner material 45 described above with reference to FIG. 5.

In the embodiment of FIG. 10, the materials 28 and 45 may be bothutilized as channel material of the memory cells (e.g., memory cells 30a, 30 b, 31 a and 31 b), and accordingly the liners 44, 46, 48 and 50may be all referred to as channel material liners; with liners 44 and 46being non-germanium-containing channel material liners, and with liners48 and 50 being germanium-containing channel material liners. Thegermanium-containing channel material liners are spaced from sidewalls23 and 25 of opening 27 by the non-germanium-containing channel materialliners 44 and 46 in the embodiment of FIG. 10.

The germanium-containing material 28 of liners 48 and 50 may behomogeneous, or may comprise horizontally-extending germanium gradientsof the types described above with reference to FIGS. 7-9

The structures described above may be supported by an underlyingsubstrate (not shown). The substrate may comprise semiconductor material(for example, may comprise, consist essentially of, or consist ofmonocrystalline silicon), and may be referred to as a semiconductorsubstrate. The term “semiconductor substrate” means any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials), and semiconductive materiallayers (either alone or in assemblies comprising other materials). Theterm “substrate” refers to any supporting structure, including, but notlimited to, the semiconductor substrates described above.

The integrated structures described herein may be incorporated intoelectronic systems. Such electronic systems may be used in, for example,memory modules, device drivers, power modules, communication modems,processor modules, and application-specific modules, and may includemultilayer, multichip modules. The electronic systems may be any of abroad range of systems, such as, for example, cameras, wireless devices,displays, chip sets, set top boxes, games, lighting, vehicles, clocks,televisions, cell phones, personal computers, automobiles, industrialcontrol systems, aircraft, etc.

Unless specified otherwise, the various materials, substances,compositions, etc. described herein may be formed with any suitablemethodologies, either now known or yet to be developed, including, forexample, atomic layer deposition (ALD), chemical vapor deposition (CVD),physical vapor deposition (PVD), etc.

Both of the terms “dielectric” and “electrically insulative” may beutilized to describe materials having insulative electrical properties.The terms are considered synonymous in this disclosure. The utilizationof the term “dielectric” in some instances, and the term “electricallyinsulative” in other instances, may be to provide language variationwithin this disclosure to simplify antecedent basis within the claimsthat follow, and is not utilized to indicate any significant chemical orelectrical differences.

The particular orientation of the various embodiments in the drawings isfor illustrative purposes only, and the embodiments may be rotatedrelative to the shown orientations in some applications. The descriptionprovided herein, and the claims that follow, pertain to any structuresthat have the described relationships between various features,regardless of whether the structures are in the particular orientationof the drawings, or are rotated relative to such orientation.

The cross-sectional views of the accompanying illustrations only showfeatures within the planes of the cross-sections, and do not showmaterials behind the planes of the cross-sections in order to simplifythe drawings.

When a structure is referred to above as being “on” or “against” anotherstructure, it can be directly on the other structure or interveningstructures may also be present. In contrast, when a structure isreferred to as being “directly on” or “directly against” anotherstructure, there are no intervening structures present. When a structureis referred to as being “connected” or “coupled” to another structure,it can be directly connected or coupled to the other structure, orintervening structures may be present. In contrast, when a structure isreferred to as being “directly connected” or “directly coupled” toanother structure, there are no intervening structures present.

Some embodiments include an integrated structure having a stack ofalternating dielectric levels and conductive levels, and havingvertically-stacked memory cells within the conductive levels. An openingextends through the stack. Channel material is within the opening andalong the memory cells. At least some of the channel material containsgermanium.

Some embodiments include an integrated structure comprising, along across-section, a stack of alternating dielectric levels and conductivelevels, vertically-stacked memory cells within the conductive levels, anopening extending through the stack, germanium-containing channelmaterial liners within the opening and along the memory cells, and aninsulator-filled hollow within the opening and between thegermanium-containing liners.

Some embodiments include an integrated structure comprising, along across-section, a stack of alternating dielectric levels and conductivelevels, vertically-stacked memory cells within the conductive levels, anopening extending through the stack, non-germanium-containing channelmaterial liners along sidewalls of the opening and along the memorycells, germanium-containing channel material liners within the openingand along the non-germanium-containing material liners, and aninsulator-filled hollow within the opening and between thegermanium-containing liners.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

We claim:
 1. An integrated structure comprising: a stack of alternatingdielectric levels comprising a dielectric material and conductive levelsthat comprise a conductive material that physically contacts thedielectric material; vertically-stacked memory cells within theconductive levels, each of the vertically stacked memory cellscomprising a charge trapping region, the dielectric material of thedielectric levels extending over and beneath the charge trapping regionacross an entirety of a width of the charge trapping region; an openingextending through the stack, the opening having a sidewall extendingvertically continuously from top to bottom of the opening; and a channelliner material within the opening and along the memory cells anddirectly against the dielectric material of the dielectric levels; and agermanium-comprising channel material within the opening and spaced fromthe sidewall by the channel liner material, the germanium-comprisingchannel material having a horizontally-extending gradient of germanium,and comprising at least one dopant; the dopant being p-type, n-type ori-type and being present in a horizontally-extending dopant gradient. 2.The integrated structure of claim 1 wherein a concentration of germaniumin the horizontally-extending gradient of germanium increases in adirection and wherein a concentration of dopant in thehorizontally-extending dopant gradient increases along the samedirection.
 3. The integrated structure of claim 1 wherein aconcentration of germanium in the horizontally-extending gradienthorizontally-extending gradient of germanium increases in a firstdirection and a concentration of dopant in the horizontally-extendingdopant gradient increases in a second direction that opposes the firstdirection.